Images stored in box of vapor

Emma Woollacott, 30th May 2012

Giving a different meaning to data storage in the cloud, scientists have succeeded in storing a miniature movie in a room-teperature atomic vapor.

Scientists at NIST's Joint Quantum Institute have stored two letters of the alphabet in a small cell filled with rubidium (Rb) atoms, tailored to absorb and later re-emit messages on demand. It's the first time two images have simultaneously been reliably stored in a non-solid medium and then played back.

Stretching a definition just a little, the researchers say that because they can store and replay two separate images, or 'frames', a few micro-seconds apart, the whole sequence can qualify as a feat of cinematography.

The team believes that its atomic method will be useful for storing and processing quantum information.

"It is very exciting because images and movies are familiar to everyone. We want to go to the quantum level," says physicist Quentin Glorieux.

"If we manage to store quantum information embedded in an image or maybe in multiple images, that could really hasten the advent of a quantum network/internet."

The atomic storage medium is a narrow cell some 20 centimeters long, needed for a quantum process called gradient echo memory (GEM), a protocol for storage that was pioneered at the Australian National University.

The image is stored by being absorbed in atoms at any one particular place in the cell, depending on whether those atoms are exposed to three carefully tailored fields: the electric field of the signal light, the electric field of another 'control' laser pulse, and a magnetic field adjusted to be different along the length of the cell. This makes the Rb atoms - each behaving like a magnet itself - move about.

When the image is absorbed into the atoms in the cell, the control beam is turned off.

Image readout occurs in a sort of reverse process. The magnetic field is flipped to a contrary orientation, the control beam turned back on, and the atoms start to precess in the opposite direction. Eventually those atoms reemit light, thus reconstituting the image pulse, which proceeds on its way out of the cell.

"The big thing here is that this allows us to do images and do pulses (instead of individual photons) and it can be matched (hopefully) to our squeezed light source, so that we can soon try to store "quantum images" and make essentially a random access memory for continuous variable quantum information," says physicist Paul Lett.